3.5.3 Single participant interventions
A single participant intervention study, studies the effects of an intervention in the case of one person, with the aim of establishing those elements of the intervention which would work with the majority of people. This is because the method assumes that in all important respects, all human beings are the same, and the effects of the intervention in one case should be the same in all cases. It is a method that belongs to objectivity.
Box 18: Featured method
Single participant experimental designs
Single participant experimental designs are used to assess the effectiveness of an intervention on a case by case basis. What may be effective for some people may not work well for others, and given the heterogeneous nature of people with reading difficulties it would seem appropriate to adopt a single case strategy to the design and assessment of interventions for this and similarly varied samples. This approach is also used in other areas of psychological intervention such as psychotherapy and psychoanalysis.
There are a variety of designs that are used within this method, one of them being the ABAB Design (see Figure 7).
A baseline measure is taken several times before the intervention is introduced (A), and then during the intervention itself (B). The intervention is then withdrawn for a sustained period (A) and reintroduced (B). This alternating pattern enables the researcher to see if the intervention has any genuine effect on the individual, whether the benefit is reliable (i.e. is it reproduced the second time the intervention is applied), and whether it has a continued benefit after the intervention is withdrawn. The participant also acts as his or her own ‘control’ in a design of this nature. This design gives a richer picture of what is going on than a simple pre-post test design would.